[MITgcm-support] Resources for generating curvilinear grid for MITgcm (displaced-pole Arctic)

[Jean-Michel Campin]

Hi Sam,

There is a way to "rotate" the lat-lon grid to move the N & S pole elsewhere.
this is done by setting the 3 rotation angle: phiEuler, thetaEuler, psiEuler

>From PARAMS.h:
C     rotateGrid      :: rotate grid coordinates to geographical coordinates
C                        according to Euler angles phiEuler, thetaEuler, psiEuler

And the piece of code that does the rotation is: rotate_spherical_polar_grid.F
called from: ini_spherical_polar_grid.F

Cheers,
Jean-Michel

On Sun, Feb 22, 2026 at 02:58:49PM -0500, Sam Phillips wrote:
> Hi all,
> 
> I'm setting up a barotropic, wind-forced Arctic Ocean simulation on a
> displaced-pole curvilinear grid (pole at -40E, 75N over Greenland), NX=1530
> NY=520 at ~10.7km resolution, single vertical level just as a baseline.
> 
> I'm running into what appear to be grid generation problems - my mitgrid
> metrics show implausible values (dxF and dxC with minimums around 22m on a
> nominally 10.7km grid, dyC constant everywhere, rAz reaching zero) that I
> believe are causing immediate cg2d divergence.
> 
> Before going further with debugging, I'd like to go back to basics and
> generate a proper mitgrid file. I'm currently using a Python-based workflow
> but I'm open to anything. A few specific questions:
> 1. Is there a recommended tool or workflow for generating displaced-pole
> curvilinear grids for MITgcm?
> 2. Are there example mitgrid files or grid generation scripts for Arctic or
> regional curvilinear configurations that I could use as a reference?
> Googling hasn't proven very helpful.
> 3. Is there anything specific to watch out for when the displaced pole
> falls over land (Greenland in my case) in terms of how the grid metrics
> behave near the seam?
> 
> Any pointers to scripts, papers, or configurations that have worked for
> similar domains would be very helpful.
> 
> Thanks,
> Sam

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